The present invention relates to a novel locking device for a rotatable operating lever. More particularly the invention relates to a device for locking a rotatable operating lever which, like the throttle operating lever of a remote control unit for marine engines, must be frequently turned during navigation and also locked to a suitable turned position to propel the boat at a constant speed.
FIGS. 1 and 2 show a conventional device for locking such a rotatable operating lever. The locking device comprises a driven member 40 mounted at its shaft portion 42 on a casing 36 and turnable in the direction of an arrow F or arrow B, a lever 30 attached to the outer side of the casing 36 by the shaft 42 and rotatable by a handle 32 in the direction of an arrow D or arrow E, a locking member 44 having a tapered portion 46 and an internally threaded portion 48 non-rotatably in engagement with an externally threaded outer peripheral portion of the lever 30, a locking plate 50 fixedly attached to the casing 36 and formed with a circular arc V-groove 52 concentric with the shaft 42, retaining means 56 for preventing the lever 30 from slipping off the driven member 40, and an end shaft 54 of a control cable having one end pivoted to the driven member 40 and the other end connected, for example, to an unillustrated throttle member. When rotated in one direction, the lever 30 brings the tapered portion 46 into pressing contact with the V-grooved portion 52, whereby the lever 30 can be locked to the desired position. Since the throttle lever 30 adapted for use with marine engines is usually locked to an approximately definite turned position (for example, to the position indicated in two-dot-and-dash lines in FIG. 1), so as to propel the boat economically at a constant speed, the V-grooved portion 52 wears away rapidly at this position. When the lever 30 is slightly rotated in the other direction to unlock the tapered portion 46 from such a locally worn portion of the locking plate 50 and the tapered portion 46 is slightly moved away from the V-groove 52 of the plate 50, the tapered portion 46 will sometimes come into pressing contact with an unworn part of the V-grooved portion 52 upon turning the lever, thus preventing the turn of the lever 30 at an undesired position. The lever 30 can then be turned to another unworn position only after the lever 30 has been further rotated in the other direction. If the lever 30 is thus inadvertently lockable at an undesired position, the lever 30 is not operable as quickly as is desired. A dangerous situation, such as a collision, could then result.
The conventional device has another drawback. When the tapered portion 46 is held pressed against a slanting portion on either side of the worn grooved portion, the vibration of the boat is liable to shift the tapered portion 46 to the lowest position of the worn grooved portion. Thus the lever will shift abruptly.